Exchange Anisotropy and Antiferromagnetic Coupling in NiFe/FeMn/Co Trilayers

The exchange bias fields at the interfaces of NiFe/FeMn/Co trilayers with thin Co layers were investigated using the ferromagnetic resonance technique. It has been found that the angular dependences of the in-plane resonance fields for both NiFe and Co layers exhibit the effect of the unidirectional anisotropy field. No evidence of uniaxial anisotropy was observed for the thin Co layers and the values for the exchange bias field are in agreement with values given by magnetization measurements. For the NiFe layer, the angular dependence of the in-plane resonance field gives evidence of a small uniaxial magnetic anisotropy, attributed to interface texture and antiferromagnetic coupling between NiFe and Co layers.